I. Field of the Invention
This invention pertains to transportation networks and more particularly to a method and apparatus for controlling the movement of a vehicle through a transportation network.
II. Description of the Prior Art
A need for a fuel efficient economical rapid transit system exists. The current state of mass transit systems includes busses and railway systems as well as underground subway trains and elevated trains and the like. All of these systems attempt to move large numbers of people in large vehicles. As a result, the vehicle must stop at a plurality of stations to allow passengers to embark and disembark as desired. Therefore, the effective average speed of the vehicle is reduced by the constant. stopping and starting. Most riders make numerous stops between their point of origin and their intended destination.
A personal rapid transit system would eliminate several of the above problems since each vehicle carries a small number of passengers desiring to go to the same destination. As a result, each vehicle bypasses all intermediate stops. Therefore, the average speed of the vehicle can be greatly increased while its maximum speed remains the same. Delays associated with stopping at intermediate points are eliminated. The advantages of a personal rapid transit system have been known to those skilled in the art. However, construction of such a system and its method of operation have been elusive.
A personal rapid transit system having individual cars which move about a common track or guideway is shown in my commonly assigned U.S. Pat. No. 4,522,128 issued June 11, 1985. Also, further improvements and details in the vehicle and guideway are shown and described in commonly assigned U.S. Pat. Nos. 4,671,185 issued June 9, 1987; and 4,665,830 issued May 19, 1987 and U.S. Pat. No. 4,665,829 issued May 19, 1987 on application Ser. No. 890,881 continuation of Ser. No. 463,951 filed Feb. 4, 1983, now abandoned. The aforementioned patents teach a vehicle sized for a small number of passengers which is moved along a guideway. The aforesaid U.S. Pat. No. 4,665,830 enumerates several articles which generally discuss transit systems.
The development of a personal rapid transit system presents certain problems with respect to the apparatus and method for controlling movement of vehicles from an origin to a destination. For example, a personal rapid transit system having vehicles which are to be guided by computers must have a method of operation which is sufficiently flexible for the vehicle to be able to direct itself to any possible destination station from any possible origin station. Possible solutions to the method and apparatus for controlling movement of such vehicles would include having each vehicle with on-board computers which have a complete memory of the entire transportation network and is pre-programmed such that at any given origin station it knows the proper direction to take at any one of a plurality of junction points throughout the network on way to a destination station. However, such a scheme for operating the control of a mass transit system requires a substantial amount of programming logic. Also, once the logic has been established, it is not easily modified. Therefore, such a system is not sufficiently flexible in the event of congestion in any specific location on the network to adapt to the congestion to re-route vehicles. Also, if the network is expanded or otherwise modified, the logic programs must be modified and rewritten. This is a costly practice and may make a personal rapid transit system prohibitively expensive.
An alternative to on-board memorization of the transit network is to have centralized memorization with a central computer controlling movement of the vehicles with means for providing communication between the vehicle and the central logic unit. Information to be transmitted would include information from the vehicle indicating its location and desired destination. The central computer would transmit to the vehicle the sequence of turns necessary at all approaching junctions needed to arrive at the desired destination. The vehicle would necessarily have an on-board microprocessor to accept the variety of information received from the central logic unit and use this information to effect operation of on-board switching devices. The problem associated with the extensive use of a centralized computer is that a substantial amount of information must be exchanged between the vehicle and the central computer on a regular basis. As the amount of necessary information transfer increases, the possibility of an error in tranmission increases. One possible source of such errors would be noise in the transmission.
It is recognized that the probability of error in a transmission of information can be extremely low if the amount of information being transferred is minimal. However, in transit systems that have a plurality of stations and a wide variety of routes connecting the stations, the amount of information which would be transmitted to a vehicle as to the sequence of turns it must take to achieve its destination can become extremely large such that the possibility for error in a transmission is not acceptable.